The present invention relates to a method of and an apparatus for stopping the operation of a production line in case of an emergency, and more particularly to a method of and an apparatus for localized emergency shutdown of a production line including self-propelled carriages for transferring workpieces along a power feed line and automatic machines disposed in respective working zones or work stations along the production line for assembling and machining the workpieces, the method and apparatus being capable of stopping the operation of a self-propelled carriage and an automatic machine in case of emergency only in the working zone which is subjected to an operation failure.
The automobile industry has one of the most advanced automatic production facilities. The automobile production lines are combined with various industrial robots which replace manual labor and effect various operations such as assembling, coating, welding, and other processes.
The automated production lines are also associated with automated workpiece feed means. One recent example of such automatic workpiece feed means is the use of self-propelled carriages instead of conventional conveyor lines. Self-propelled carriages independently run along desired tracks in a factory. They can more easily adapt themselves to modified track layouts than the conveyor lines, and do not take up a large space. Therefore, the space available in the factory can be utilized effectively.
Self-propelled carriages run to transfer workpieces from one station to another along a production line while being supplied with electric power from a power feed line extending along the production line.
Heretofore, the power feed line is arranged to extend through all production stations or working zones along the production lines. If an unexpected serious trouble occurs in one production station, then the power feed line has to be cut off to stop the operation of the self-propelled carriage and the automatic machine or robot in the faulty production station, and hence all the production stations are shut off of necessity. Once the automobile assembly line is shut off to stop the manufacturing operation, it takes a considerable time to restore the production line back to normal operation. Such assembly line shutdown results in quite a large loss of money since each automobile product would otherwise be completed very rapidly in a matter of seconds.
Japanese Laid-Open Utility Model Publication No. 61-154128 discloses a system in which a power feed line extending along a production line is divided into segments associated with respective working zones and the electric power supplies for the power feed line segments can independently be turned on and off to prevent the entire production line from being shut off.
However, since production lines have a large number of working zones or production stations, it is time-consuming and laborious to install such power feed line segments in the respective working zone and control units for independently turning on and off the power supplies for each power feed line segments. Therefore, the cost of such independently controllable power line segments is very high.